Circulating drainage system for sewage pipe installation work

ABSTRACT

A sewage by-pass discharging apparatus for sewage pipe works comprises an upstream side stop cock disposed at an upstream side of a sewage pipe laid in a working area, a downstream side stop cock disposed at a downstream side of the sewage pipe laid in the working area, a member for discharging the sewage accumulated at an upstream side from the upstream side stop cock to a downstream side from the downstream sides stop cock by bypassing the sewage pipe, a drain pipe connected to the sewage pipe laid in the working area, a drain pit connected to the drain pipe, a stop cock for preventing the sewage from flowing from the drain pit into the drain pipe, and a unit discharging the sewage reserved in the drain pit to downstream side from the downstream side stop cock. According to this structure, the working to the sewage pipe can be performed while the sewage system is maintained in a state of being utilized as usual by the residents of the respective homes.

TECHNICAL FIELD

The present invention relates to a sewage by-pass discharging apparatusfor working a sewage pipe laid under the ground, the apparatus enablingto prevent the sewage from flowing into a working area including thesewage pipe when the sewage pipe is subjected to various workings suchas cleaning, inspection, repairing, replacement or the like.

BACKGROUND ART

In general, when a sewage pipe laid under the ground is used for a longperiod of time, soil sediment, sludge, foreign material are deposited atinterior of the sewage pipe, so that it is necessary to remove thedeposited sediment, sludge and foreign material and clean the sewagepipe.

Further, the sewage pipe laid under the ground will be deteriorated withelapse of times, so that cracks and defects at joint portions of thesewage pipes are liable to occur. In particular, in a case where thesewage pipe is a Hume pipe, a bore or hole is liable to be formed due toerosion of the pipe body. Therefore, the interior of the sewage pipe isrequired to be periodically inspected and repaired, or the sewage pipeper se is required to be replaced by new one.

As described above, when the sewage pipe is subjected to variousworkings such as cleaning, inspection, repairing, replacement or thelike, various equipments and instruments for the workings are conveyedinto the sewage pipe, and workers would access into the sewage pipe toperform the working. Therefore, it is obliged for the sewage systemcontaining the objective sewage pipe to be stopped in use.

As a countermeasure for solving the afore-mentioned problems, forexample, a sewage by-pass or circulation discharging apparatus forsewage pipe works is well known as disclosed in Japanese Utility ModelPublication No. HEI 6-13890.

The conventional sewage by-pass discharging apparatus for working thesewage pipe, as shown in FIG. 15, has a structure in which a portion 1abetween a first manhole 2 and a second manhole 3 of the sewage pipe 1 isspecifically provided as the working area, and a stop cock 4 isrespectively provided to both an upstream side portion 1b and adownstream side portion 1c of the sewage pipe 1 laid in the working area1a thereby to prevent the sewage or the like from flowing into thesewage pipe 1a laid in the working area la.

Further, a suction pipe 6 of a pump 5 disposed on the ground isconnected to the upstream side portion 1b, while a delivery pipe 7 ofthe pump 5 is connected to the downstream side portion 1c, whereby thesewage or the like accumulated at upstream side from the working areaflows toward the downstream side through bypassing the working area.

According to the sewage by-pass discharging apparatus for working thesewage pipe as described above, even if the sewage system is utilized asusual, the sewage would not flow into the sewage pipe laid in theworking area. Therefore, the workings such as cleaning, inspection,repairing, replacement or the like for the sewage pipe laid in theworking area can be performed while the sewage system is utilized asusual.

However, in actual, a plurality of drain pipes are connected to thesewage pipe laid between the first manhole 2 and the second manhole 3,and the drain pipes are connected to drain pits provided at respectivehomes of residents, so that the sewage or the like discharged from aplurality of the homes would flow into the sewage pipe laid in theworking area.

Due to this situation, the respective residents of which the drain pitis connected to the sewage pipe laid in the working area are obliged tostop utilizing the sewage system during the working for the sewage pipe.

Therefore, an object of the present invention is to provide a sewageby-pass discharging apparatus for sewage pipe works capable of achievingvarious workings such as cleaning, inspection, repairing, replacement orthe like for the sewage pipe while being maintained in a state where therespective residents can utilize the sewage system as usual.

DISCLOSURE OF THE INVENTION

In order to achieve the afore-mentioned object, according to one aspectof the present invention, there is provided a sewage by-pass dischargingapparatus for sewage pipe works, comprising: an upstream side stop cockprovided at an upstream side of a sewage pipe laid in a working area; adownstream side stop cock provided at a downstream side of the sewagepipe laid in the working area; means for discharging the sewageaccumulated at an upstream side from the upstream side stop cock into adownstream side from downstream side stop cock by bypassing the sewagepipe; a drain pipe connected to the sewage pipe laid in the workingarea; a drain pit connected to the drain pipe; a stop cock forpreventing the sewage from flowing from the drain pit into the drainpipe; and means for discharging the sewage reserved in the drain pitinto the downstream side from the downstream side stop cock.

In the above structure, the apparatus may preferably have a structure inwhich both the upstream side and the downstream side stop cocksexpansively deform by being supplied with air so that an outer peripheryportion of each stop cock is press contacted to an inner peripherysurface of the sewage pipe, and each of the stop cocks is provided witha pipe so as to penetrate through the stop cock.

The apparatus may preferably have a structure in which each of theplural drain pits is provided with an auxiliary suction pipe so as to beinserted into the drain pit respectively, each of the auxiliary suctionpipes is connected to a main suction pipe which is connected to asuction side of a suction discharging equipment, so that the sewage inthe respective drain pits is discharged into the downstream side fromthe downstream side stop cock.

Further, the apparatus may preferably have a structure in which each ofthe plural drain pits is provided with an auxiliary suction pipe so asto be inserted into the drain pit respectively, each of the auxiliarysuction pipes is connected to a suction side of a suction dischargingequipment, so that the sewage in the respective drain pits is dischargedinto a downstream side from the downstream side stop cock.

It is more preferable that the apparatus further comprises means forcontrolling the respective auxiliary suction pipes so as not tosimultaneously suck the sewage.

In the above structure, it may be preferred for the apparatus to have astructure in which each of the auxiliary suction pipes is provided witha shut-off valve, the shut-off valves taking an opened position in turnat predetermined intervals of time whereby each of the auxiliary suctionpipes sucks the sewage in turn for a predetermined time.

Further, the apparatus may preferably have a structure in which each ofthe drain pits is provided with a level sensor for sensing a level ofthe sewage so as to output a signal when the level reaches to apredetermined level, and the shut-off valve provided to the auxiliarysuction pipe inserted into the corresponding drain pit having the levelsensor preferentially takes an opened position when the level sensoroutputs the signal.

Furthermore, the apparatus may preferably have a structure in which theauxiliary suction pipe is provided with a float valve which takes anopened position when the level of the sewage in the drain pit becomeshigher than a predetermined level while takes a closed position when thelevel of the sewage in the drain pit becomes lower than a predeterminedlevel.

In the above structure in another aspect of this invention, there isprovided a sewage by-pass discharging apparatus for sewage pipe works,comprising: a shut-off valve provided to each of the auxiliary suctionpipes, respectively; a controller for controlling the respectiveshut-off valves so as to flake an opened or closed position; and asensor for sensing a degree of vacuum of a portion closer to a drain pitfrom the shut-off valve so as to input the degree of vacuum to thecontroller,

wherein the controller controls the shut-off valves in such a mannerthat one shut-off valve is opened while remaining shut-off valves areclosed so as to discharge the sewage in one drain pit through oneauxiliary suction pipe, and when the degree of vacuum of the oneauxiliary suction pipe becomes lower than a setting value, the oneshut-off valve is closed while one of the other remaining shut-offvalves is opened in a predetermined order.

In still another aspect of the present invention, there is provided asewage by-pass discharging apparatus for sewage pipe works, comprising:a shut-off valve provided to each of the auxiliary suction pipes,respectively; a controller for controlling the respective shut-offvalves so as to take an opened or closed position; and a sensor formeasuring a degree of vacuum of a portion between the respective drainpit and the suction discharging equipment so as to input the degree ofvacuum to the controller,

wherein the controller controls; the shut-off valves in such a mannerthat one shut-off valve is opened while the remaining shut-off valvesare closed so as to discharge the sewage in one drain pit through oneauxiliary suction pipe, and when the degree of vacuum detected by thesensor becomes lower than a setting value, the one shut-off valve isclosed while one of the other remaining shut-off valves is opened in apredetermined order.

Furthermore, the apparatus may preferably have a structure in which thecontroller controls the shut-off valves in such a manner that oneshut-off valve is opened while the remaining shut-off valves are closedso as to discharge the sewage in one drain pit through one auxiliarysuction pipe, and when the degree of vacuum detected by the sensorbecomes lower than a setting value, the one shut-off valve is closed,and when the degree of vacuum detected by the sensor is returned to thesetting value, one of the other remaining shut-off valves is opened.

In still another aspect of the present invention, there is provided asewage by-pass discharging apparatus for sewage pipe works, comprising:a shut-off valve provided to each of the auxiliary suction pipes,respectively; a controller or controlling the respective shut-off valvesso as to take an opened or closed position; a sensor for measuring adegree of vacuum of a portion between a suction opening of therespective auxiliary suction pipes provided to the drain pits and thesuction discharging equipment; and a level sensor for sensing a level ofthe sewage in the drain pit to input a signal into the controller whenthe level reaches to a predetermined level,

wherein the controller controls the shut-off valves in such a mannerthat when the signal from the level sensor is not inputted, one shut-offvalve is opened in a predetermined order while the remaining shut-offvalves are closed so as to discharge the sewage in one drain pit throughone auxiliary section pipe, and when the degree of vacuum detected bythe sensor becomes lower than a setting value, the one shut-off valve isclosed while one of the other remaining shut-off valves is opened in apredetermined order and

wherein the controller controls the shut-off valves in such a mannerthat when the signal from the level sensor is inputted, the shut-offvalve in an opened state at the time is closed while the shut-off valveprovided to the auxiliary suction pipe connected to the drain pit havingthe level sensor is opened, and when the degree of vacuum detected bythe sensor becomes lower than a setting value, the one shut-off valve isclosed while one of the other remaining shut-off valves is opened in apredetermined order.

In still another aspect of the present invention, there is provided asewage by-pass discharging apparatus for sewage pipe works, comprising:a shut-off valve provided to each of the auxiliary suction pipes,respectively; a controller for controlling the respective shut-offvalves so as to take an opened or closed position; a sensor formeasuring a degree of vacuum of a portion between of the respectiveshut-off valves and the suction discharging equipment; and a levelsensor for measuring a level of the sewage in the drain pit to input asignal into the controller when the level reaches to a predeterminedlevel,

wherein the controller has:

a first function of controlling the shut-off valves in such a mannerthat when the degree of vacuum measured by the sensor becomes lower thana predetermined value, the one shut-off valve is closed while one of theother remaining shut-off valves is opened in a predetermined order;

a second function of controlling the shut-off valves in such a mannerthat when a sucking time exceeds a predetermined time in a while thedegree of vacuum would not become lower than a predetermined value, theone shut-off valve is closed while one of the other remaining shut-offvalves is opened in a predetermined order; and

a third function of preferentially controlling the shut-off valvesregardless the first and second functions in such a manner that when thesignal from the level sensor is inputted into the controller, theshut-off valve in an opened state at this time is closed while theshut-off valve provided to the auxiliary suction pipe connected to thedrain pit having the level sensor is opened, and when the degree ofvacuum detected by the sensor becomes lower than a setting value, orwhen a sucking time exceeds a predetermined time in a while the degreeof vacuum would not become lower than a setting value, the one shut-offvalve is closed while one of the other remaining shut-off valves isopened in turn.

Advantages of the sewage by-pass discharging apparatus for sewage pipeworks having such structures according to the present invention are asfollows.

According to the present invention, the stop cock is provided to boththe upstream and downstream side portions of the sewage pipe laid in theworking area, respectively, so that the sewage or the like flowing inthe sewage pipe would not flow into the sewage pipe laid in the workingarea. Further, there is provided with the stop cock for preventing thesewage from flowing out of the drain pit of the respective homes to thedrain pipe, so that the sewage or thus like flowing from the drain pitof the respective homes would not flow into the sewage pipe laid in theworking area. In addition, the sewage or the like accumulated at theupstream side of the sewage pipe laid in the working area is dischargedinto the downstream side by bypassing the working area, and the sewageor the like accumulated in the drain pits of the respective homes isdischarged into the downstream side from the sewage pipe laid in theworking area.

As a result, the workings such as cleaning, inspection, repairing,replacement or the like for the sewage pipe can be performed while thesewage system is in a state of being utilized as usual by the residentsof the respective homes.

In addition, the bodies of both the upstream side and the downstreamside stop cocks are press contacted to inner periphery surfaces of thesewage pipes, excellent sewage-sealing property can be obtained, and thesewage or the like can be sucked or discharged by using the pipepenetrating through the up-stream side and the downstream side stopcocks.

Further, a length of the auxiliary suction pipe to be inserted into therespective drain pits can be shortened, and only one elongated mainsuction pipe can be disposed in a corner portion of a road, so thatthose suction pipes would not obstruct passengers walking on the road orthe working area.

Furthermore, an initial setup for the working can be finished only byconnecting the respective suction pipes to a suction side of the suctiondischarging equipment, so that the working can be simplified.

In addition, each of the auxiliary pipes is constructed so as not tosimultaneously suck the sewage or the like, so that a capacity of thesuction discharging equipment can be reduced, whereby a small-sizedsuction discharging equipment is available.

Furthermore, only one of the respective auxiliary pipes performs thesucking operation in turn for a predetermined time, so that a capacityof the suction discharging equipment can be further reduced, whereby asuction discharging equipment having a smaller size is be available.

In addition, in a case where the discharging amounts of the sewage fromthe respective homes are greatly varied, the sewage contained in a drainpit dealing with the large discharging amount of the sewage ispreferentially sucked, so that there is no fear of the sewage filling upand overflowing the drain pit.

Further, in order to control the sewage level, it is sufficient toprovide a float valve, so that the structure of the apparatus can besimplified, and a complicated control is not necessary.

In addition, according to the present invention, when the sewage in onedrain pit is discharged through one auxiliary suction pipe and thesewage amount in the drain pit is decreased whereby the auxiliarysuction pipe sucks air, a degree of vacuum measured by the sensorbecomes lowered whereby the shut-off valve provided to the auxiliarysuction pipe is closed while one of the other remaining shut-off valvesis opened in a predetermined order, so that the sewage in one of theremaining drain pits is discharged.

As a result, the sewages in a plurality of the drain pits can bedischarged at every drain pit, so that the suction discharging equipmentcan be Constructed in a small size. Further, the auxiliary suction pipeis provided with the shut-off valve and the sensor, so that it issufficient to connect the auxiliary suction pipe to the drain pit, thussimplifying the operation thereof.

Further, the sensor is provided to the auxiliary suction pipe at aportion close to the drain pit and apart from the shut-off valve, sothat when the shut-off valve is closed, the degree of vacuum measured bythe sensor will become to an atmospheric pressure (760 mmHg), wherebythe sensor would not malfunction.

In addition, a distance from the sensor to the drain pit is short whilea distance from the sensor to the suction discharging equipment is long.Therefore, when the amount of the sewage in the drain pit is decreasedand the auxiliary suction pipe sucks air whereby a value measured by thesensor becomes lower than a setting value, the sewage exists at aportion of the auxiliary suction pipe close to the suction dischargingequipment, so that the degree of vacuum of the suction dischargingequipment would riot be lowered. In addition, when the value measured bythe sensor becomes lower than a setting value, the shut-off valve ispromptly closed.

As a result, there is no case of lowering the vacuum degree of thesuction discharging equipment, the sewage in the respective drain pitscan be effectively discharged.

Further, in the present invention, the sensor is provided at a portionbetween the respective drain pits and the suction discharging equipment,so that only one sensor can be commonly used.

In addition, according to the present invention, when the sewage in onedrain pit is discharged through one auxiliary suction pipe and theauxiliary suction pipe sucks air, the shut-off valve provided to theauxiliary suction pipe is closed. Subsequently, when the degree ofvacuum is returned to a predetermined value, one of the remainingshut-off valves is opened in a predetermined order, so that the sewagein one of the remaining drain pits is discharged.

Accordingly, during a time period from a time when the degree of vacuummeasured by the sensor becomes lower than the setting value to a timewhen the degree of vacuum becomes to a predetermined value, each of theshut-off valves is in a closed state, so that the degree of vacuum isreturned to the predetermined value in a short period of time.

Furthermore, according to the present invention, in a case where asignal from the level sensor is not inputted to the controller, thesewage in one drain pit is discharged through one auxiliary suction pipein a predetermined order. While, when the amount of sewage in the drainpit is decreased and the auxiliary suction pipe sucks air, the degree ofvacuum measured by the sensor becomes lower than a setting value and theshut-off valve provided to the auxiliary suction pipe is closed, whileone of the other remaining shut-off valves is opened in a predeterminedorder whereby the sewage in one of the other remaining drain pits isdischarged.

In addition, in a case where the sewage in one drain pit is dischargedin a predetermined order by opening one of the shut-off valves in apredetermined order as described above, when the sewage level in onedrain pit reaches to a constant level, a signal from the level sensor isinputted to the controller. In this case, the controller controls therespective shut-off valves in such a manner that the shut-off valve inan opened state at that time is closed while the shut-off valvecorresponding to the level sensor is opened whereby the sewage in thedrain pit having a sewage level higher than the constant value isdischarged , and when the degree of vacuum measured by the sensorbecomes lower than the setting value, the shut-off valve is closed andthe remaining shut-off valves are opened in a predetermined orderthereby to return to the opening-closing controlling operation as in thecase where a signal from the level sensor is not inputted to thecontroller as described above.

As a result, the sewage in a plurality of the drain pits can bedischarged at every drain pit in a predetermined order, so that thesuction discharging equipment can be constructed in a small size.Further, when the sewage is accumulated in a drain pit so as to exceed aconstant height, the sewage in the drain pit is preferentiallydischarged regardless of the order described above, so that there is nofear of the sewage in the drain pit overflowing.

Further, according to the present invention, in a case where the sewagein the respective drain pits is discharged in a predetermined order, thedischarging operation in accordance with the degree of vacuum of thedrain pit is preferentially performed. Even if the degree of vacuum isnot lower than the setting value, when the sucking time exceeds apredetermined time, the shut-off valve is closed and one of the otherremaining shut-off valves is opened in a predetermined order thereby todischarge the sewage in one of the other remaining drain pits.

In addition to this operation, when the signal from the level sensor isinputted to the controller, the shut-off valve in an opened state atthat time is closed while the shut-off valve corresponding to the levelsensor is opened, whereby the sewage in the drain pit of which sewagelevel exceeds the setting value is preferentially discharged.

As a result, even if the sensor fails to detect the degree of vacuum ofa part of the drain pits, after the sucking operation is continued for apredetermined time, the sewage discharging operation is performed inturn from the remaining one of the drain pits to another drain pit in apredetermined order, so that the sewage can be securely discharged fromall of the drain pits.

In addition to the operation described above, the sewage in the drainpit of which sewage level exceeds the constant level is preferentiallydischarged, so that the sewage would not overflow from the drain pit,and the sewage can be securely discharged from all of the drain pits.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more apparent and more easily beunderstood from the following detailed description when taken inconjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexamples.

Further, the embodiments shown in the accompanying drawings are not forspecifying or limiting the scope of the present invention, but formerely making the explanation and understanding of the invention moreeasily.

In the accompanying drawings:

FIG. 1 is a longitudinal view showing a first embodiment of a sewageby-pass discharging apparatus for sewage pipe works according to thepresent invention.

FIG. 2 is an explanatory view showing a suction discharging equipment tobe used in the present invention.

FIG. 3 is a cross sectional view showing an upstream side stop cock or adownstream side stop cock to be used in the present invention.

FIG. 4 is a cross sectional view showing a drain pit to be used in thepresent invention.

FIG. 5 is a plan view showing a first embodiment of a drainage route ofthe sewage in a drain pit to be used in the present invention.

FIG. 6 is a diagram of a control circuit to be used in the presentinvention.

FIG. 7 is a cross sectional view showing an embodiment of a drain pit inwhich a float valve is attached to an auxiliary suction pipe to be usedin the present invention.

FIG. 8 is a plan view showing a second embodiment of a drainage route ofthe sewage in a drain pit to be used in the present invention.

FIG. 9 is a longitudinal view showing a second embodiment of a sewageby-pass discharging apparatus for working a sewage pipe according to thepresent invention.

FIG. 10 is an explanatory view showing a third embodiment of a drainageroute of the sewage in a drain pit to be used in the present invention.

FIG. 11 is another embodiment of a diagram of a control circuit to beused in the present invention.

FIG. 12 is an explanatory view showing a fourth embodiment of a drainageroute of the sewage in a drain pit to be used in the present invention.

FIG. 13 is still another embodiment of a diagram of a control circuit tobe used in the present invention.

FIG. 14 is a flow-chart explaining opening and closing operations of asolenoid shut-off valve, which actuates in accordance with a time and avacuum pressure, to be used in the apparatus according to the presentinvention.

FIG. 15 is a cross sectional view showing a conventional sewagedischarging apparatus for working a sewage pipe.

BEST MODE FOR EMBODYING THE INVENTION

The preferred embodiments of the sewage by-pass discharging apparatusfor sewage pipe works according to the present invention will bedescribed hereunder with reference to the accompanying drawings.

In the drawings, FIG. 1 is a view showing a first embodiment of a sewageby-pass discharging apparatus for sewage pipe works according to thepresent invention. In this sewage by-pass discharging apparatus forsewage pipe works, a first sewage pipe 11 is opened to a first manhole10. A second sewage pipe 12 is opened to the first manhole 10 and alsoto a second manhole 13. A third sewage pipe 14 is opened to the secondmanhole 13 and also to a third manhole 15. A fourth sewage pipe 16 isopened to the third manhole 15. The respective sewage pipes arecommunicated to each other through the respective manholes and laidunder the ground. The sewage or the like flows from the first sewagepipe 11 toward the fourth sewage pipe 16.

In a case where the third sewage pipe 14 is specified to be a workingarea, an upstream side stop cock 17 is provided to the upstream side ofthe third sewage pipe 14 i.e., an outlet side of the second sewage pipe12 opened to the second manhole 13. Further, a downstream side stop cock18 is provided to the downstream side of the third sewage pipe 14 i.e.,an inlet side of the fourth sewage pipe 16 opened to the third manhole15. Accordingly, the sewage or the like flowing from the upstream sidesewage pipe would not flow into the third sewage pipe 14 as the workingarea.

By the way, the reason why the stop cock is not provided to both inletand outlet sides of the third sewage pipe 14 but is provided to both theoutlet side of the second sewage pipe 12 and the inlet side of thefourth sewage pipe 16, is as follows. Because, when workers carry outthe working for the third sewage pipe 14, the workers are required toaccess into the sewage pipe through the second manhole 13 and the thirdmanhole 15.

On the ground, there is provided with a controlling system comprising asuction discharging equipment 20, a controlled-type compressor 21 and acontroller 22 or the like.

As shown in FIG. 2, the suction discharging equipment 20 comprises atank 23, a vacuum suction pump 24 and a delivery pump 25, and theequipment 20 performs so that the vacuum suction pump 24 sucks air inthe tank 23 and the sewage or the like is sucked into the tank 23through a suction pipe 26, whereby the sewage or the like in the tank 23is delivered to a drain pipe 27.

The controller 22 controls the control-type compressor 21, the vacuumsuction pump a4, the delivery pump 25 and a solenoid shut-off valve orthe like as described later on.

An inlet port of the suction pipe 26 connected to the suctiondischarging equipment 20 is provided at the upstream side from theupstream side stop cock 17, while an outlet port of the drain pipe 27 isprovided at the downstream side from the downstream side stop cock 18.According to this structure, the sewage or the like flowing into thesecond sewage pipe 12 can flow into the fourth sewage pipe 16 bybypassing the third sewage pipe 14, thus operating the third sewage pipe14 without stopping the working of the sewage system.

As shown in FIG. 3, each of the upstream side stop cock 17 and thedownstream side stop cock 18 comprises a ring-shaped body 31 having ahollow portion composed of flexible materials such as rubber or thelike, a pipe 33 inserted into a central penetration bore 32 formed tothe body 31, a pair of press plates 34 contacted to the body 31 by beingscrewed with both end portions of the pipe 33 in a longitudinaldirection, and a nozzle 35 attached to one of the paired press plates34, the nozzle 35 being connected to the compressor 21 described above.

According to the structure described above, when the compressor 21 isstarted and air is supplied to the hollow portion 30 of the body 31through the nozzle 35, the body 31 is expansively deformed so that anouter periphery portion of the body 31 is press contacted to an innerperiphery surface of the sewage pipe. As a result, an excellent sewagesealing property can be achieved.

In addition, the suction pipe 26 is connected to the pipe 33 of theupstream side stop cock 17, while the drain pipe 27 is connected to thepipe 33 of the downstream side stop cock 18.

A plurality of drain pipes 40 Ere connected to the third sewage pipe 14.As shown in FIG. 4, each of the drain pipes 40 is connected to outlets42 of the drain pits 41 for the respective homes. A discharging pipe 44connected to a kitchen, a toilet, a bath room or the like is connectedto an inlet 43 of the drain pit 41. According to this structure, thesewage discharged from the respective homes flows into the third sewagepipe 14 through the drain pipe 40.

When a working for the third sewage pipe 14 is carried out, as indicatedin FIG. 4 by a virtual line, a stop cock 45 is provided to the outlet 42of the drain pit 41 thereby to prevent the sewage or the like fromflowing into the drain pipe 40. Further, the sewage or the like flowinginto the drain pit 41 is discharged through the auxiliary suction pipe46 by inserting the auxiliary suction pipe 46 into the drain pit 41.

In a case where the stop cock 45 is provided or a case where theauxiliary suction pipe 46 is inserted into the drain pit 41, a cover 47is removed.

As shown in FIG. 5, each of the auxiliary suction pipes 46 is connectedto one main suction pipe 49 through the shut-off valve 48, for example,a solenoid shut-off valve 48, respectively. The main suction pipe 49 isconnected to the suction pipe 26 or the tank 23. In this regard, each ofthe auxiliary suction pipes 46 may be connected to the suction pipe 26or connected to the tank 23, respectively.

FIG. 5 shows a case where the residents' homes are located along bothsides of the sewage pipe and the drain pits 41 are also provided to bothsides of the sewage pipe, so that two main suction pipes 49 are requiredto be provided. However, in a case where the residents' homes arelocated along only one side of the sewage pipe, only one main suctionpipe 49 is provided. Accordingly, as a matter off course, the two mainsuction pipes 49 may be collected to form one suction pipe.

As shown in FIG. 6, each of the solenoid shut-off valves 48 takes aclosed position a by the action of a spring 50 while takes an openedposition b when a solenoid thereof is energized arid excited. Therespective solenoids 51 are electrically controlled by the controller22.

For example, as shown in FIG. 4, a level sensor 52 such as float switchor the like for outputting a signal when the sewage level in the drainpit 41 reaches to a constant value is provided to the respectiveauxiliary suction pipes 46 and the signal from the level sensor 52 isinputted to the controller 22.

The controller 22 energizes the respective solenoids 51 of the solenoidshut-off valves 48 in turn at a predetermined time intervals, so thatone of the solenoid shut-off valves 48 takes an opened position b inturn for a predetermined period of time. Further, when the signal fromthe level sensor 52 is inputted to the controller 22, the solenoid 51 Ofthe solenoid shut-off valve 48 provided to the auxiliary suction pipe 46connected to the drain pit 41 corresponding to the level sensor 52 ispreferentially energized.

According to this structure, the sewage is sucked from any one of theplurality of the drain pits 41, so that a sucking power can be reducedin comparison with a case where the sewage in the respective drain pits41 is simultaneously sucked, whereby the size of the vacuum suction pump24 can be reduced.

By the way, the apparatus can be also constructed in such a manner thatthe level sensor 52 is not provided and the solenoids 51 of the solenoidshut-off valves 48 are energized in turn at a predetermined timeintervals so that one of the solenoid shut-off valves 48 takes an openedposition b in turn for a predetermined period of time.

Further, as shown in FIG. 7, the apparatus can be also constructed sothat a float valve 53 is provided to a top end portion of the auxiliarysuction pipe 46 whereby the float valve 53 is opened when the sewagelevel in the drain pit 41 becomes to a predetermined level or more,while the float valve 53 is closed when the sewage level becomes lowerthan a predetermined height.

The float valve 53 is assembled so that a valve 54 is opened or closedby the action of a float 55. According to the structure described above,the solenoid shut-off valve 48 is not required.

When a starting signal from a start switch 56 is inputted to thecontroller 22, the controller 22 drives a vacuum suction pump 24 and adelivery pump 25, while when a stopping signal from a stop switch 57 isinputted to the controller 22, the controller 22 stops the operation ofthe vacuum suction pump 24 and the delivery pump 25.

FIG. 8 shows a second embodiment of an apparatus for discharging thesewage in the drain pit 41. An exclusive suction discharging equipment20 for exclusively sucking the sewages in the drain pits 41 is providedso as to discharge the sewage into a drain pipe 27. In a case shown inFIG. 8, the suction discharging equipment 20 is provided to both sidesof the sewage pipe. However, only one suction discharging equipment canbe also commonly used.

According to the structure described above, the sucking and dischargingof the sewage from the sewage pipe and the sucking and discharging ofthe sewage from the drain pit 41 are performed by each of the suctiondischarging equipments, thus discharging a large amount of sewage or thelike.

In this case, the sewage can be also directly discharged into a manholeat a portion of downstream side from the third manhole 15 by using theexclusive suction discharging equipment 20.

As shown in FIG. 1, a submerged pump, for example, a submerged grinderpump 60 is provided in the first manhole 10, and a delivery pipe of thispump 60 is connected to the drain pipe 27. Accordingly, the sewage orthe like flowing out from the first sew-age pipe 11 are delivered to thedischarging pipe 27, so that the sewage or the like would not so muchflow into the second sewage pipe 12. Therefore, the vacuum suction pump24 having a small size becomes usable.

That is, the sewage or the like flowing out from the drain pits of therespective homes flows into the second sewage pipe 12 through the drainpipe 40 and is then sucked by the suction pipe 26 and discharged.

By the way, a screen 62 is provided to an inlet side of the secondsewage pipe 12.

In addition, as shown in FIG. 9, the apparatus may also be constructedso that a stop cock 63 having no pipe inserted into the hollow portionfor discharging the sewage is provided to a side portion of the thirdmanhole to which the fourth sewage pipe 16 is opened, the side portionbeing a portion of the sewage pipe 16 into which the sewage flows. Dueto this structure, the sewage or the like from the fourth sewage pipe 16in the downstream side would not flow backward so as to flow into thethird sewage pipe 14 as the working area. Further, a discharging pipe 27is provided to the fourth manhole 64 which is a downstream side from thestop cock 63.

According to this structure, the structure of the stop cock 63 can besimplified and it becomes easy to manufacture the stop cock 63.

Though not shown, also similarly in an upstream side inlet port, theapparatus may be constructed so that a stop cock having no pipe insertedinto the hollow portion for discharging the sewage is, located to adownstream side portion from the pipe for sucking the sewage of theupstream side.

Hereunder, an explanation will be started with respect to a secondembodiment of the controller for opening or closing the shut-off valves48, for example, the solenoid shut-off valve 48.

As shown in FIG. 10, the solenoid shut-off valve 48 is provided to eachauxiliary suction pipe 46 for sucking the sewage in each drain pit 41,each of the auxiliary suction pipes 46 is connected to the main suctionpipe 49, and the main suction pipe 49 is connected to an inside of atank 23 of the suction discharging equipment 20.

A sensor 70 for measuring a decree of vacuum is provided to a portion ofeach auxiliary suction pipe 46, the portion being close to the drain pit41 from the solenoid shut-off valve 48. As shown in FIG. 11, valuesmeasured by each of the sensors 70 are inputted into the controller 22.

When a starting signal from a start switch 56 is inputted to thecontroller 22, the controller 22 drives a vacuum suction pump 24 and adelivery pump 25, so that an inside of the tank 23 is formed to bevacuum. For example, the degree of vacuum is set to about 60 mmHg to 0mmHg. Simultaneously, the controller 22 energizes a solenoid 51 of oneof the solenoid shut-off valves 48 so that the valve 48 takes an openedposition b.

According to this operation, the sewage in one of the drain pit 41 issucked into the tank 23 through the auxiliary suction pipe 46 and themain suction pipe 49, then the sewage is discharged by the delivery pump25.

When the sewage amount in one of the drain pits 41 is decreased and oneof the auxiliary suction pipe 46 sucks air, a degree of vacuum in theoutstanding auxiliary suction pipe 46 becomes lower than that of tank23. The degree of vacuum in the auxiliary suction pipe 46 is measured bythe sensor 70 and inputted to the controller 22.

When the degree of vacuum measured by the sensor 70 becomes lower than asetting value, for example, 50 mmHg or less, the controller 22 stopsenergizing the solenoid 51 so that the corresponding solenoid shut-offvalve 48 takes a closed position a. Simultaneously, the controller 22energizes a solenoid 51 of one of the other solenoid valves 48 so thatthe corresponding solenoid shut-off valve 48 takes an opened position b,whereby the sewage in one of the other drain pit 41 is discharged in thesame manner as described above.

When the sewage amount in one of the other drain pit 41 is decreased andthe degree of vacuum detected by the sensor 70 becomes lower than thesetting value, the controller 22 stops energizing the solenoid 51 of thesolenoid shut-off valve 48 so that the valve 48 takes a closed positiona. Then, a solenoid 51 of subsequent one of the other solenoid shut-offvalve 48 is energized so that the valve 48 takes an opened position b,whereby the sewage in the subsequent one of the other drain pit 41 isdischarged. By repeating the sequential operations described above inturn, the sewages in all of the drain pits 41 are discharged.

As a result, the sewage in a plurality of the drain pits 41 can bedischarged at every drain pit, so that the vacuum suction pump 24 can beconstructed in a small size. Further, the auxiliary suction pipe 46 isprovided with the sensor 70, so that it is sufficient to connect theauxiliary suction pipe 46 to the drain pit 41, thus simplifying theoperation thereof.

Further, the sensor 70 is provided to the auxiliary suction pipe 46 at aportion close to the drain pit 41 and apart from the solenoid shut-offvalve 48, so that when the solenoid shut-off valve 48 takes a closedposition a, the degree of vacuum measured by the sensor 70 will becometo an atmospheric pressure (760 mmHg), whereby the solenoid shut-offvalve 48 would not malfunction.

In addition, a distance from the sensor 70 to the drain pit 41 is shortwhile a distance from the sensor 70 to the tank 23 is long. Therefore,when the amount of the sewage in the drain pit 41 is decreased and theauxiliary suction pipe 46 sucks air, and accordingly, a value measuredby the sensor 70 becomes lower than a setting value, the sewage existsat a portion of the auxiliary suction pipe 46 close to the main suctionpipe 49 and the main suction pipe 49, so that the degree of vacuum inthe tank 23 would not be lowered. In addition, when the value measuredby the sensor 70 becomes lower than a setting value, the solenoidshut-off valve 48 promptly takes a closed position a.

As described above, there is no case of lowering the vacuum degree inthe tank 23, so that the sewage in the respective drain pits 41 can beeffectively discharged.

As indicated by a solid line in FIG. 12, the sensor 70 may be disposedto a portion of each auxiliary suction pipes 46, respectively, theportion being closer to tank 23 from the solenoid shut-off valve 48.Further, as indicated by a virtual line in FIG. 12, one sensor 70 may becommonly located to a portion of the main suction pipes 49. Furthermore,one sensor 70 may be located to the tank 23.

In this case, when the degree of vacuum measured by the sensor 70becomes lower than a setting value, the controller stops energizing thesolenoid 51 of one of the solenoid shut-off valves 48 so that the valve48 takes a closed position a. Then, after the degree of vacuum measuredby the sensor 70 returns to a predetermined value, the solenoid of oneof the other solenoid shut-off valves 48 is energized so as to take anopened position b.

That is, in a case where the sensor 70 is provided for a portion closerto the tank 23 from one of the solenoid shut-off valve 48, the solenoidshut-off valve 48 takes an opened position b and the sewage in one ofthe drain pit 41 is discharged, and in this state, when the suction pipesucks air to thereby lowering the degree of vacuum measured by thesensor, the degrees of vacuum in the other auxiliary suction pipes 46,the main suction pipe 49 and the tank 23 are lowered. Accordingly, oneof the other solenoid shut-off valves 48 takes the closed position a.Then, after the degree of vacuum measured by the sensor 70 returns to apredetermined value, the solenoid 51 of one of the other solenoidshut-off valves 48 is energized so as to take an opened position b.

The control for opening or closing the shut-off valve, for example, thesolenoid valve 48 can be also performed by using the sensor 70 formeasuring the degree of vacuum described above and a level sensor 52 foroutputting a signal when a sewage level in the drain pit 41 shown inFIG. 4 reaches a constant height.

More concretely, as shown in FIG. 13, the degree of vacuum measured bythe sensor 70 is inputted to the controller 22 as well as the signalfrom the level sensor 52 is inputted to the controller.

Furthermore, in a case where a signal from the level sensor 52 is notinputted to the controller 22, in the same manner as described above,one of the solenoid shut-off valves 48 is opened in a predeterminedorder while the remaining solenoid shut-off valves 48 are closed,whereby the sewage in one drain pit is discharged through one auxiliarysuction pipe. When the degree of vacuum measured by the sensor 70becomes lower than a setting value, the solenoid shut-off valve isclosed, while one of the remaining shut-off valves is opened in apredetermined order, whereby the sewage in one of the remaining drainpits 41 is discharged in turn.

In addition, in a case where the sewage in one drain pit 41 isdischarged in a predetermined order as described above, when a signalfrom the level sensor 52 is inputted to the controller 22, thecontroller 22 controls the respective solenoid shut-off valves 48 insuch a manner that the current conduction to a solenoid 51 now in anenergized state is stopped, whereby the corresponding solenoid shut-offvalve 43 takes a closed position a.

At the same time, the controller 22 energizes the solenoid 51 of thesolenoid shut-off valve 48 disposed to the auxiliary suction pipe 46connected to the drain pit 41 corresponding to the Level sensor 52 whichoutputs the signal to the controller 22, so that the valve 48 takes anopened position b whereby the sewage in the drain pit 41 described aboveis discharged.

When the degree of vacuum measured by the sensor 70 provided to theauxiliary suction pipe 46 of the drain pit 41 in charge of dischargingthe sewage becomes lower than the setting value, the current conductionto the solenoid 51 is stopped so that the solenoid shut-off valve 48takes a closed position a. Then, in accordance with the order set in theopening-closing operation by the sensor 710, a solenoid 51 of asubsequent solenoid shut-off valve 48 next to the solenoid shut-offvalve 48 taking a closed position a is energized so that the outstandingvalve 48 takes an opened position b.

As described above, when the signal from the level sensor 52 is inputtedto the controller, the sewage in the drain pit 41 provided with thelevel sensor 52 is preferentially discharged prior to the sewage in thedrain pit taking charge of discharging the sewage in a predeterminedorder, the sewage in the drain pit 41 would not overflow.

In addition, the sewage in one drain pit 41 among a plurality of thedrain pits 41 can be also discharged by combining the followingoperations: i.e., an operation for energizing the respective solenoids51 of the shut-off valves 48, for example, the solenoid shut-off valves48 in turn in a predetermined order; an operation for stopping theenergizing of this solenoid 51 and for energizing the solenoid 51 of thesubsequent solenoid shut-off valve 48 when the degree of vacuum measuredby the sensor 70 becomes lower than the setting value or the degree ofvacuum measured by the sensor 70 would not become lower than the settingvalue even after a predetermined time has passed; and an operation forenergizing the solenoid 51 by means of the level sensor 52 foroutputting the signal when the sewage level in the drain pit 41 reachesa constant height.

For example, the controller 22 shown in FIG. 13 is constructed so as tohave the following three functions: i.e., a first function of energizingthe solenoids 51 of a plurality of the solenoid shut-off valves 48 in apredetermined order which is previously set; a second function ofenergizing the solenoid 51 on the basis of the degree of vacuum measuredby the sensor 70; and a third function of energizing the solenoid 51 onthe basis of a signal from a sensor, for example, the level sensor 52shown in FIG. 4.

The second function described above will be explained more concretely.In a case where the solenoids 51 are energized in a predetermined orderso that the corresponding solenoid shut-off valve 48 takes an openedposition b in turn and the sewage in one drain pit 41 is discharged,when the degree of vacuum measured by the sensor 70 corresponding to thedrain pit 41 becomes lower than the setting value or the degree ofvacuum measured by the sensor 70 would not become lower than the settingvalue even after a predetermined time has passed, the solenoid 51 isimmediately stopped being energized and another solenoid 51 of asubsequent solenoid shut-off valve 48 is energized.

Above sequential operation can be expressed by a flow-chart as shown inFIG. 14.

The third function described above will be explained more concretely.

As described above, in a case where the sewage in one drain pit 41 isdischarged in ai predetermined order, when the signal from the levelsensor 52 is inputted to the controller 22, the controller 22 controlsthe respective shut-off valves in such a manner that the currentconduction to the solenoid 51 now in an energized state at that time isstopped so that the solenoid shut-off valve 48 takes a closed positiona.

At the same time, the controller 22 energizes the solenoid 51 of thesolenoid shut-off valve 48 provided to the auxiliary suction pipe 16connected to the drain pit 41 corresponding to the level sensor 52 whichoutputs the signal to the controller 22, so that the valve 48 takes anopened position b whereby the sewage in the drain pit 41 is discharged.

When the degree of vacuum measured by the sensor 70 disposed to theauxiliary suction pipe 46 of the drain pit 41 taking charge ofdischarging the sewage becomes lower than the setting value, the currentconduction to the solenoid 51 is stopped so that the solenoid shut-offvalve 48 takes a closed position a. Then, in accordance with the orderset in the opening-closing operation by the sensor 70, the solenoid 51of a subsequent solenoid shut-off valve 48 next to the solenoid shut-offvalve 48 taking a closed position a is energized so that the outstandingvalve 48 takes an opened position b.

Although the present invention has been described with reference to theexemplified embodiments, it will be apparent to those skilled in the artthat various modifications, changes, omissions, additions and othervariations can be made in the disclosed embodiments of the presentinvention without departing from the scope or spirit of the presentinvention. Accordingly, it should be understood that the presentinvention is not limited to the described embodiments, and shall includethe scope specified by the elements defined in the appended claims andrange of equivalency of the claims.

We claim:
 1. A sewage by-pass discharging apparatus for sewage pipeworks, comprising: an upstream side stop cock disposed at an upstreamside of a sewage pipe laid in a working area; a downstream side stopcock disposed at a downstream side of the sewage pipe laid in theworking area; means for discharging the sewage accumulated at anupstream side from the upstream side stop cock to a downstream side fromdownstream side of the downstream side stop cock by bypassing the sewagepipe; a drain pipe connected to the sewage pipe laid in the workingarea; a drain pit connected to the drain pipe; a stop cock forpreventing the sewage from flowing from the drain pit into the drainpipe; and means for discharging the sewage reserved in the drain pit tothe downstream side from the downstream side stop cock.
 2. A sewageby-pass discharging apparatus for sewage pipe works according to claim1, wherein both said upstream and downstream side stop cocks expansivelydeform by being supplied with air so that an outer periphery portion ofeach of the stop cocks is press contacted to an inner periphery surfaceof said sewage pipe, and each of said stop cocks is provided with a pipepenetrating through said stop cock.
 3. A sewage by-pass dischargingapparatus for sewage pipe works according to claim 1 or 2, wherein eachof a plurality of drain pits is provided with an auxiliary suction pipeso as to be inserted into said drain pit, respectively, and each of saidauxiliary suction pipes is connected to a main suction pipe which isconnected to a suction side of a suction discharge equipment, so thatthe sewage in the respective drain pits is discharged to the downstreamside from said downstream side stop cock.
 4. A sewage by-passdischarging apparatus for sewage pipe works according to claim 1 or 2,wherein each of a plurality of drain pits is provided with an auxiliarysuction pipe so as to be inserted into the drain pit, respectively, andeach of said auxiliary suction pipes is connected to a suction side of asuction discharge equipment, so that the sewage in the respective drainpits is discharged to the downstream side from said downstream side stopcock.
 5. A sewage by-pass discharging apparatus for sewage pipe worksaccording to claim 3, further comprising means for controlling therespective auxiliary suction pipes so as not to simultaneously suck thesewage.
 6. A sewage by-pass discharging apparatus for sewage pipe worksaccording to claim 5, wherein each of said auxiliary suction pipes isprovided with a shut-off valve, said shut-off valves taking an openedposition in turn at predetermined intervals of time whereby each of saidauxiliary suction pipes sucks the sewage in turn for a predeterminedtime.
 7. A sewage by-pass discharging apparatus for sewage pipe worksaccording to claim 6, wherein each of said drain pits is provided with alevel sensor for sensing a level of the sewage so as to output a signalwhen the sewage level reaches to a predetermined level, and the shut-offvalve provided to the auxiliary suction pipe inserted into thecorresponding drain pit having the level sensor preferentially takes anopened position when the level sensor outputs the signal.
 8. A sewageby-pass discharging apparatus for sewage pipe works according to claim5, wherein said auxiliary suction pipe is provided with a float valvewhich takes an opened position when the level of the sewage in saiddrain pit becomes higher than a predetermined level while takes a closedposition when the level of the sewage in the drain pit becomes lowerthan a predetermined level.
 9. A sewage by-pass discharging apparatusfor sewage pipe works according to claim 5, further comprising ashut-off valve provided to each of the auxiliary suction pipes,respectively, a controller for controlling the respective shut-offvalves so as to take the opened or closed position, and a sensor forsensing a degree of vacuum of a portion closer to the drain pit from theshut-off valve so as to input the degree of vacuum to thecontroller,wherein said controller controls the shut-off valves in sucha manner that one of shut-off valves is opened while remaining shut-offvalves are closed so as to discharge the sewage in one drain pit throughone auxiliary suction pipe and when the degree of vacuum of the oneauxiliary suction pipe becomes lower than a setting value, the oneshut-off valve is closed while one of the other remaining shut-offvalves is opened in a predetermined order.
 10. A sewage by-passdischarging apparatus for sewage pipe works according to claim 5,further comprising a shut-off valve provided to each of said auxiliarysuction pipes, respectively, a controller for controlling the respectiveshut-off valves so as to take an opened or closed position, and a sensorfor measuring a degree of vacuum of a portion between the respectivedrain pit and the suction discharging equipment so as to input thedegree of vacuum to the controller,wherein said controller controls theshut-off valves in such a manner that one of shut-off valves is openedwhile the remaining shut-off valves are closed so as to discharge thesewage in one drain pit through one auxiliary suction pipe and when thedegree of vacuum detected by the sensor becomes lower than a settingvalue, the one shut-off valve is closed while one of the other remainingshut-off valves is opened in a predetermined order.
 11. A sewage by-passdischarging apparatus for sewage pipe works according to claim 10,wherein said controller controls the shut-off valves in such a mannerthat one of the shut-off valves is opened while the remaining shut-offvalves are closed so as to discharge the sewage in one drain pit throughone auxiliary suction pipe, and when the degree of vacuum detected bythe sensor becomes lower than a setting value, the one shut-off valve isclosed, and when the degree of vacuum detected by the sensor is returnedto the setting value, one of the other remaining shut-off valves isopened.
 12. A sewage by-pass discharging apparatus for sewage pipe worksaccording to claim 5, further comprising a shut-off valve provided toeach of said auxiliary suction pipes, respectively, a controller forcontrolling the respective shut-off valves so as to take an opened orclosed position, a sensor for measuring a degree of vacuum of a portionbetween a suction opening of the respective auxiliary suction pipesdisposed to the drain pits and the suction discharging equipment, and alevel sensor for sensing a level of the sewage in the drain pit to inputa signal into the controller when the level reaches to a predeterminedlevel,wherein said controller controls the shut-off valves in such amanner that when the signal from the level sensor is not inputted, oneof the shut-off valves is opened in a predetermined order while theremaining shut-off valves are closed so as to discharge the sewage inone drain pit through one auxiliary suction pipe and when the degree ofvacuum detected by the sensor becomes lower than a setting value, theone shut-off valve is closed while one of the other remaining shut-offvalves is opened in a predetermined order, and wherein said controllercontrols the shut-off valves in such a manner that when the signal fromthe level sensor is inputted, the shut-off valve in an opened state atthat time is closed while the shut-off valve provided to the auxiliarysuction pipe connected to the drain pit having the level sensor isopened and when the degree of vacuum detected by the sensor becomeslower than a setting value, the one shut-off valve is closed while oneof the other remaining shut-off valves is opened in a predeterminedorder.
 13. A sewage by-pass discharging apparatus for sewage pipe worksaccording to claim 5, further comprising a shut-off valve provided toeach of said auxiliary suction pipes, respectively, a controller forcontrolling the respective shut-off valves so as to take an opened orclosed position, a sensor for measuring a degree of vacuum of a portionbetween of the respective shut-off valves and the suction dischargingequipment, and a level sensor for measuring a level of the sewage in thedrain pit to input a signal into the controller when the level reachesto a predetermined level,wherein the controller has: a first function ofcontrolling the shut-off valves in such a manner that when the degree ofvacuum measured by the sensor becomes lower than a predetermined value,the one shut-off valve is closed while one of the other remainingshut-off valves is opened in a predetermined order, a second function ofcontrolling the shut-off valves in such a manner that when a suckingtime exceeds a predetermined time in a while the degree of vacuum wouldnot become lower than a predetermined value, the one shut-off valve isclosed while one of the other remaining shut-off valves is opened in apredetermined order, and a third function of preferentially controllingthe shut-off valves regardless of the first and second functions in sucha manner that when the signal from the level sensor is inputted into thecontroller, the shut-off valve in an opened state at that time is closedwhile the shut-off valve provided to the auxiliary suction pipeconnected to the drain pit having the level sensor is opened and whenthe degree of vacuum detected by the sensor becomes lower than a settingvalue, or when a sucking time exceeds a predetermined time in a whilethe degree of vacuum would not become lower than a setting value, theone shut-off valve is closed while one of the other remaining shut-offvalves is opened in turn.